package org.apache.lucene.util;

/**
 * Copyright 2004 The Apache Software Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.io.ObjectStreamException;
import java.io.Serializable;
import java.io.StreamCorruptedException;
import java.util.HashMap;
import java.util.Map;

/**
 * A serializable Enum class.
 */
public abstract class Parameter implements Serializable {
    static Map allParameters = new HashMap();

    private String name;

    private Parameter() {
        // typesafe enum pattern, no public constructor
    }

    protected Parameter(String name) {
        // typesafe enum pattern, no public constructor
        this.name = name;
        String key = makeKey(name);

        if (allParameters.containsKey(key))
            throw new IllegalArgumentException("Parameter name " + key + " already used!");

        allParameters.put(key, this);
    }

    private String makeKey(String name) {
        return getClass() + " " + name;
    }

    public String toString() {
        return name;
    }

    /**
     * Resolves the deserialized instance to the local reference for accurate
     * equals() and == comparisons.
     * 
     * @return a reference to Parameter as resolved in the local VM
     * @throws ObjectStreamException
     */
    protected Object readResolve() throws ObjectStreamException {
        Object par = allParameters.get(makeKey(name));

        if (par == null)
            throw new StreamCorruptedException("Unknown parameter value: " + name);

        return par;
    }

}
